1. Field of the Invention
The invention relates to a clutch disk assembly having a variable hysteresis mechanism for uses in an automotive vehicle, ship or the like.
2. Description of the Prior Art
A conventional clutch assembly has a variable hysteresis mechanism which changes the hysteresis at multiple stages of operation. However, a clutch assembly of this type has a flight or series of steps between a first hysteresis stage and a second hysteresis and is utilized in a driving system in which noises and vibrations are produced according to variations in engine torque. On the other hand, a traditional clutch disk assembly with a variable hysteresis mechanism is also known which changes the hysteresis in smooth non-stepwise action according to the change of a torsion angle.
As prior art, Japanese Patent Laid Open No. 58637(1983) is shown in FIGS. 7 and 8. In this conventional clutch disk assembly, a cam mechanism is disposed between the sub plate 75 and the thrust plate (control member) 77, and spring load is varied with the cam mechanism in response to the torsion angle. Namely, the torque-variation transmitted to the sub plate 75 is changed to an axial displacement through the cam mechanism (cam 75d and cam face 77d) and the axial displacement changes the load of cone spring 78, thereby increasing and decreasing the hysteresis.
However, in this mechanism, the spring load is always acting on the cam and, due to the sliding movement of the cam it is easily abraded. Further, the hysteresis is generated from a low level to a higher level by the variable hysteresis, so that when the cam is abraded, the load of the spring 78 changes. As a result, the stable hysteresis can not be obtained.